Influence of Mn on crystal structure and thermoelectric properties of GeTe compounds

Lee, J. K.; Oh, Min‐Wook; Kim, B. S.; Min, Bok Ki; Lee, H. W.; Park, S. D.

doi:10.1007/s13391-014-4149-8

Cited by 63 publications

(61 citation statements)

References 21 publications

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“…The temperature-dependent total thermal conductivity κ total derived from D and C p using equation (5) is presented in Figure 6a. At 773 K, the κ total value for Ge 0 for other GeTe based materials, which was ascribed to the second-order phase transition from rhombohedral to cubic phase 33,36,37,39,44 . This transition temperature decreases from 673 K to 573 K with increase in Ag content from 1 to 6 mol%.…”

Section: Figure 2 Temperature-dependent (A) Electrical Conductivity mentioning

confidence: 98%

Impact of Coinage Metal Insertion on the Thermoelectric Properties of GeTe Solid-State Solutions

et al. 2017

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A comprehensive study on the thermoelectric effect of Ag substitution in GeTe solid solutions, a congenital base for high efficient TAGS-m [(GeTe) m (AgSbTe 2 ) 100-m ] thermoelectric materials, was performed. First-principles calculations were carried out to probe the changes arising from doping on the electronic band structure of GeTe, which exhibits a rhombohedral (r) structure at temperatures lower than 700 K. Aliovalent Ag substitution in GeTe increases the hole concentration and decreases the thermoelectric figure of merit (zT) due to the reduction of the Seebeck coefficient, which is ascribed mainly to the lowering of the Fermi level together with the loss of band degeneracy. Band structure and effective mass calculations of these doped materials also point to a soaring contribution from several hole pockets in the valence band. First-principles calculations carried out with two other group-11 transition metals (Cu, Au) reveal that silver substitution has the lowest impact on the thermopower of r- Page 1 of 32 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 GeTe. A mean zT of ∼0.85 at 773 K is achieved for Ge 1-x Ag x Te (x ≤ 0.04) solid solutions. The study highlights the limits in doping just a coinage metal to GeTe and recapitulates the need for pair substitution to enhance the thermoelectric properties of GeTe-based solid-state solutions.

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Section: Figure 2 Temperature-dependent (A) Electrical Conductivity mentioning

confidence: 98%

Impact of Coinage Metal Insertion on the Thermoelectric Properties of GeTe Solid-State Solutions

et al. 2017

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“…In pristine materials with optimized carrier concentrations, the lower-energy offset between these two bands in PbTe (0.17 eV 29,30,35 at 300 K) compared with that in SnTe (0.3-0.4 eV 32,34 at 300 K) leads to a much higher-power factor (30 μW cm − 1 K − 2 36 ) for PbTe than that for SnTe (20 μW cm − 1 K − 2 37 ). For GeTe, the available literature shows a power factor of ∼ 40 μW cm − 1 K − 2 , [38][39][40][41] which is the highest among the three compounds. The underlying origin of this phenomenon, however, is ambiguous, to our best knowledge.…”

Section: Introductionmentioning

confidence: 98%

Electronic origin of the high thermoelectric performance of GeTe among the p-type group IV monotellurides

et al. 2017

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PbTe and SnTe in their p-type forms have long been considered high-performance thermoelectrics, and both of them largely rely on two valence bands (the first band at L point and the second one along the Σ line) participating in the transport properties. This work focuses on the thermoelectric transport properties inherent to p-type GeTe, a member of the group IV monotellurides that is relatively less studied. Approximately 50 GeTe samples have been synthesized with different carrier concentrations spanning from 1 to 20 × 10 20 cm − 3 , enabling an insightful understanding of the electronic transport and a full carrier concentration optimization for the thermoelectric performance. When all of these three monotellurides (PbTe, SnTe and GeTe) are fully optimized in their p-type forms, GeTe shows the highest thermoelectric figure of merit (zT up to 1.8). This is due to its superior electronic performance, originating from the highly degenerated Σ band at the band edge in the low-temperature rhombohedral phase and the smallest effective masses for both the L and Σ bands in the high-temperature cubic phase. The high thermoelectric performance of GeTe that is induced by its unique electronic structure not only provides a reference substance for understanding existing research on GeTe but also opens new possibilities for the further improvement of the thermoelectric performance of this material.

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“…In addition to the phase-change memory function, GeTe exhibits various intriguing properties, such as a many-valley band structure1415, superconductivity1617, and thermoelectricity1819202122. The p -type charge carriers in this system are unintentionally self-doped due to Ge vacancies23.…”

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confidence: 99%

Heat-Treatment-Induced Switching of Magnetic States in the Doped Polar Semiconductor Ge1−xMnxTe

Kriener

Nakajima

Kikkawa

et al. 2016

Sci Rep

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Cross-control of a material property - manipulation of a physical quantity (e.g., magnetisation) by a nonconjugate field (e.g., electrical field) – is a challenge in fundamental science and also important for technological device applications. It has been demonstrated that magnetic properties can be controlled by electrical and optical stimuli in various magnets. Here we find that heat-treatment allows the control over two competing magnetic phases in the Mn-doped polar semiconductor GeTe. The onset temperatures Tc of ferromagnetism vary at low Mn concentrations by a factor of five to six with a maximum Tc ≈ 180 K, depending on the selected phase. Analyses in terms of synchrotron x-ray diffraction and energy dispersive x-ray spectroscopy indicate a possible segregation of the Mn ions, which is responsible for the high-Tc phase. More importantly, we demonstrate that the two states can be switched back and forth repeatedly from either phase by changing the heat-treatment of a sample, thereby confirming magnetic phase-change-memory functionality.

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Influence of Mn on crystal structure and thermoelectric properties of GeTe compounds

Cited by 63 publications

References 21 publications

Impact of Coinage Metal Insertion on the Thermoelectric Properties of GeTe Solid-State Solutions

Impact of Coinage Metal Insertion on the Thermoelectric Properties of GeTe Solid-State Solutions

Electronic origin of the high thermoelectric performance of GeTe among the p-type group IV monotellurides

Heat-Treatment-Induced Switching of Magnetic States in the Doped Polar Semiconductor Ge1−xMnxTe

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